Motorcycle electronic Gear Indicator

This is a new design for a universal gear indicator that can be fitted to any motorcycle as an aftermarket accessory. Its main advantage is that its operation depends entirely on the gear shift lever movement, instead of connecting to speedometer and tachometer sensors (found in expensive commercial devices), which are rarely available in older motorcycles. It consists of a main circuit including a 7?segment LED indicator, two Hall sensors that are attached to the motorcycle frame, and a small magnet placed on the gear shift lever.
Motorcycle electronic Gear Indicator - schematic

A successful circuit build will do a self-test when connected solely to 12V power (pins TO_POWER_1 and TO_POWER_2), by cycling through all digits on the 7-segment display (see video below). After the self-test, the current gear will be shown and can be changed by the shift lever movement. Note that a gear is changed when the magnet's south pole is drawn away from the sensor (north pole will not work). Moreover, if a neutral gear is detected (from the neutral switch connected to TO_POWER_4), the display resets to zero (also acting as a self-calibrating feature if anything goes wrong). Finally, when the power is turned off, the last shown gear is stored in the MCU's flash EEPROM and restored when the device is turned on again. The main circuit is based on an AVR ATTINY25/45/85 microcontroller, which reads the signals of the two Hall sensors and the neutral switch and outputs the current gear number to a 7?segment LED indicator, through a 4026 counter/decoder. The source code is written in AVR-GCC (WinAVR) and can be programmed with the default fuses using an AVR programmer (default : ATTINY25 microcontroller and USBTiny programmer). Moreover, the constant TOP_GEAR 5 should be changed to 6 for six-gear motorbikes. The suggested implementation for the main circuit is a small size, double-sided PCB, with SMD packages for the microcontroller and the decoder ICs. The 7-segment LED is placed in a secondary PCB, connected...

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